UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) September 25, 2003

STRUCTURED ASSET SECURITIES CORPORATION (as Depositor under the Trust Agreement, dated July 1, 2003, providing for the issuance of Mortgage Pass-Through Certificates, Series 2003-21)
(Exact name of registrant as specified in its charter)

Delaware
(State or other jurisdiction
of incorporation)

333-102489
(Commission
File Number)

74-2440850
(IRS Employer
Identification No.)

745 Seventh Avenue, 7th Floor, New York, New York
(Address of principal executive offices)

10019
(Zip Code)

Registrant's telephone number, including area code 212-526-7000

(Former name or former address, if changed since last report.)

Item 5. Other Events and Regulation FD Disclosure.

This current report on Form 8-K relates to the monthly distribution reported to the holders of Structured Asset Securities Corporation Mortgage Pass-Through Certificates Series 2003-21, which was made on September 25, 2003.

Item 7. Financial Statements and Exhibits.

99.1 Monthly distribution report pursuant to Section 4.03 of the Trust Agreement for the distribution on September 25, 2003.
(Exhibit No. Description)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

LASALLE BANK NATIONAL ASSOCIATION, IN ITS CAPACITY AS TRUSTEE UNDER THE POOLING AND SERVICING AGREEMENT ON BEHALF OF STRUCTURED ASSET SECURITIES CORPORATION, REGISTRANT

Date: September 26, 2003

By: /s/ Russell Goldenberg
Russell Goldenberg
Group Senior Vice President

STRUCTURED ASSET SEC CORP MORT PASS THR CERTS SER 2003-21 8-K